| Author | Message | ||
     Chevycummins |
Sorry the video and sound is not that great, the dyno is in a trailer. http://www.youtube.com/watch?v=ihB33v8I-dM  Hp 118.4 Tq 67.1 ft-lbs | ||
| Xb9 |
Sounds good, but what happen to the HP? | ||
| Skylerxb12r |
Please tell me that dyno is notorious for being 15 hp low... PLEASE! Im about to go finish the welding on my tip after performing the same mod. I threw up in my mouth a bit when i read this post. Im sure there are some fueling issues generated by the "new" muffler that may be causing the decrease in power. Come on ECM Spy!  | ||
| Geforce |
What elevation/altitude are you? Considering both HP and TQ numbers are scaled back so much do you live up in the mountains? | ||
| Glitch |
You didn't do a base line run? | ||
| Kttemplar |
I just got my bike dynoed at Liberty Buell HD with the stock exhaust and everything. The only modification I have made is removing the solenoid. The max HP was 128.92 and the max Torque was 73.57.  Mike | ||
| Jpfive |
My dyno run back in May was done with the solenoid in place, and I was not getting 100% throttle consistently. It turned 125.22HP/71.67ft-lb even so. I am looking forward to a rematch with that dyno in two weeks - with the solenoid gone this time. Jack | ||
| Chevycummins |
Let me explain the numbers. The first two higher runs were with just premium gas, the other 3 runs were with the miracle fuel additive that a sales person is pushing for our university vehicles. It took away about 10hp. I don't think we will be buying any of his product. It was 75 degrees out and I think my elevation is about 700ft. The dyno run was a little low. Looks like there is lots of room for improvement. The solenoid has been removed. It has a K&N filter. | ||
| Jerseyguy |
I got mine done at Liberty as well and it was 128.7 hp. No mods other than the solenoid removed. | ||
| Xb9 |
Don't you think the huge dip or hole on the high end may be caused by the exhaust mods? Look at the shape of both HP and Torque curves on the top end (+8.5K) It looks like it killed it on the top end. | ||
| Dalton_gang |
Looks kinda ugly to me.  Sorry Chevy. | ||
| Chevycummins |
It might not be the exhaust mod that killed my top end. I have always had a fuel pressure code that comes up. Its been checked out 3 times and can never find anything wrong. I checked the fuel pressure and didn't like what I saw. This bike has been more problematic than most. Its just my luck. There is still a fuel problem with my bike and that may be why I have such low Hp numbers. Too bad I didn't do a dyno run before any mods to compare the results. Please post your dyno results if you have any. I find it interesting to see them. I hope my fuel problem gets worse so it can be diagnosed and repaired. | ||
| Xb9 |
Try this (from Tech Tip TT390, 9/18/08): While in data mode (Diag mode) monitor the fuel pressure, it should come up to pressure at key on without engine running and slowly drop pressure, if it rapidly drops off there is an issue. Also, I've seen if you start the bike before the check engine light goes off at key on, you can set a fuel system error P code. | ||
| Xb9 |
Have you taken it to the dealer to have them check it for the fuel sys. code? | ||
| Chevycummins |
The dealer has checked it 3 times. "No problem found" even though the fuel pressure code comes back in a couple of days. I never try to start the bike before the gauge sweep is done and lights go off. I checked the pressure in Diag and with a manual gauge connected. I found that the pressure drops very quickly after the pump shuts off. Not all the time though. I also found that the fuel pressure goes up and down 8psi or more even with a steady throttle. When the bike is shut off the fuel pump will prime up every 10 seconds over and over again for the 10 minutes until the ecm shuts off. When I first got the bike the fuel pump would only prime maybe 1 time in 10 minutes. I called Buell to ask them what a normal number of times the pump primes after shut off and really didn't get an answer. I asked what the spec is on the time the fuel system should hold fuel pressure after the prime and got no answer. All they told me was yes the pump will prime after the bike is shut off. I already knew that! On most fuel injected vehicles there is a spec like fuel pressure should not drop more than 10 psi in 15 min. What is it on this bike? My dealer has a dyno, should I suggest they run it at full load while testing the fuel pressure to see if it will maintain pressure under load? | ||
| Xb9 |
If it hasn't been to the dealer recently (since the service manual came out) they may have not had enough diagnostic information to go by. If the fuel pressure is dropping quickly with the test I posted above, there is a problem. The tech tip refers to a fuel system diagnostic check in the service manual to follow if that is the case. I would take it back to the dealer, refer them to the tech tip, and see if they can diagnose. If they can't find the problem, call Buell customer service and/or take it to another dealer. Bottom line it should not be setting the code, and they need to correct it. | ||
| Rfischer |
As has been commented on many times, it is VERY difficult to improve on factory exhaust designs, particularly Buell as Erik et al. are flow specialists. Without the ability to alter fuel & timing maps, the very likely result of any muffler mod will be less power and/or holes in the delivery of power. This set of dyno pulls amply demonstrates that fact. | ||
| Zac4mac |
For the time-being, I'm buying into Mike's theory that his fuel pressure is making the hole on his dyno runs. No different than running the bowl dry in the "old days". I have a hard time believing more flow makes a hole at the top. Z | ||
| Rfischer |
Ask Erik. And, yes, it is very different from "running the bowl dry in the old days." | ||
| Zac4mac |
OK, I trust your ideas, you got way more time than me at this level of performance. I'll watch and learn, thanks for patience in tutelage. Z | ||
| Xl1200r |
Zac - can't confuse more flow with better flow - sometimes more isn't better and vise versa. That said, I don't think this muffler tip mod that's slowly catching on created that hole, and if it did, it's only because the ECM can't compensate for the change in exhaust dynamics. I'll wait until his fuel pressure issue is resolved before I draw any conclusions. One thing is for sure, though - there's a problem with that bike. That's a dip in power that you'll feel, no question. | ||
| Xb9 |
My money is on the exhaust mod. correcting the top end fueling (mapping)caused by the change to exhaust flow may help it, but I don't think you will get it all back by the size of it. If it's a fuel pressure problem, then why: 1. Is it so consistent with RPM among all the runs? 2. It's making more power at 10.5K where it needs more fuel than at 8.3K where it needs less? Do some think the stock exhaust was just someone's pipe dream with all the chambers and tubes and compartments in it? That thing probably has more engineering into it than they initially had into the ECM algorithms! (sic joke, maybe not too funny) Seriously though, you just can't go cutting or altering that thing and expect it to work better. You may get more noise, but you're going to hurt the power and create problems elsewhere. | ||
| Thurstonbuell |
Buell Spec's : Tuned, tri-pass resonance chamber with integral helmholtz tuning Definition : When air is forced into a cavity, the pressure inside increases. Once the external force that forces the air into the cavity disappears, the higher-pressure air inside will flow out. However, this surge of air flowing out will tend to over-compensate, due to the inertia of the air in the neck, and the cavity will be left at a pressure slightly lower than the outside, causing air to be drawn back in. This process repeats with the magnitude of the pressure changes decreasing each time. Hope you understand all that , I dont , but if you get the general idea , you can see why you cant alter it and expect it to improve performance , it alone by design is improving your performance . They put alot of time into that ugly thing strapped to the bottom of your bike , thats what is so beautiful about it !!!!} | ||
| 1_mike |
Or...if one wants to hollow out the existing chambers...and baffle these chambers...in effect to build a home made Flow Master car muffler. Doesn't take an engineering degree to come up with a Flow Master design. Just a bit of common sense. No offense to any Flow Master designers! Mike | ||
| Chevycummins |
I guess now all we need is one of the other people that modified their exhaust to do a dyno run and post it here. That way we will know if their bike produces less power also. My bike has always seemed extra lean to me. Glowing red exhaust pipes at idle, poor throttle response at mid and upper ranges. The exhaust mod did not seem to effect the way it runs as far as I can tell. Its got to go to the dealer again for the clutch cover brake fluid leak and I will have them check the fuel system again. The P0193 code came back after the last flash in about a day. It didn't fix itself yet. The exhaust mod in my mind is temporary until their is an aftermarket exhaust that I like. I'm still looking. | ||
| Xb9 |
Interesting reading: Google 'helmholtz tuning' Guitars and Gearheads! | ||
| Chevycummins |
http://www-mime.eng.utoledo.edu/design_clinic/desi gn_expo/fall01pages/2001-04-14/Power%20Train.htm | ||
| Chevycummins |
After looking on the net I found lots of articles about helmholtz tuning for performance gains with intake manifolds. Not finding anything for exhaust except for how it cancels noise but nothing for how it increases performance by making it flow better. | ||
| Jpfive |
Chevy, what are your AFV's? Everything I see you post points to a fuel pressure problem. If your fuel pressure is low, the AFV's should be high, in an attempt to compensate for that. Jack | ||
| Diablo1 |
My dealer has a dyno, should I suggest they run it at full load while testing the fuel pressure to see if it will maintain pressure under load? Yes! If you are seeing the pressure vary 8 psi, then you have found the problem. Fuel injection maps are designed around a "regulated fuel pressure". Hook a manual gauge up and compare fuel pressure to the factory specification at various throttle openings under load. I'll bet a donut that you have low fuel pressure or low fuel flow and are going lean at full throttle at high rpm.} |
